1. Field of the Invention
This invention relates to heart disorders. More specifically, this invention relates to detecting and evaluating arrhythmia, fibrillation and related disorders by manipulation of an electrocardiogram signal.
2. Description of Related Art
Despite major advances in the diagnosis and treatment of ischemic heart disease over the past decade, a substantial number of patients each year may suffer sudden cardiac death as a consequence of ventricular fibrillation (VF). To date, no reliable predictive or preventive measures have been developed. By all outward appearances, VF is a highly complex, seemingly random phenomenon. So are other related heart disorders, including those stages in heart behavior which typically precede VF (onset of VF). Accordingly, it is difficult for automated devices to determine with any reliability that a patient is undergoing VF or onset of VF. Moreover, onset of VF may also be difficult to determine with any reliability, even for skilled medical personnel.
A method of detecting and evaluating heart disorders would therefore find wide applicability and utility. Patient monitoring devices may summon medical personnel if the patient is undergoing VF or onset of VF. Automatic devices which attempt to counter VF, e.g. automatic implantable cardiac defibrillators (AICDs) may vary their operation based on evaluation of the severity of the patient's condition. Methods for reliably evaluating the risk of VF may also have important utility in monitoring patients undergoing surgery or other critical therapy.
It has been found that some anti-arrhythmic drugs may also have a pro-arrhythmic effect in excess concentrations. For example, quinidine has been known to be toxic in this manner. A method of detecting and evaluating heart disorders would also have wide applicability and utility in determining if a patient has been subjected to a toxic (or partially toxic) dosage of a drug relating to heart condition.
Chaos theory is a recently developed field relating to phenomena which appear to be highly complex and seemingly random, but which may be described as the deterministic result of relatively simple systems. Chaos theory may have potentially wide applications in biologic and other systems involving ambiguity and uncertainty. For example, it has been conjectured that chaos theory may be valuable for describing certain natural processes, including electroencephalogram (EEG) and electrocardiogram (EKG) signals. Techniques for detecting and evaluating aspects of deterministic chaos are known in the field of chaos theory, but have found little application in the medical field.
Accordingly, there is a need for improved methods and devices for detecting and evaluating heart disorders, including ventricular fibrillation (VF) and the onset of VF.